Complementary roles of murine Na V 1.7, Na V 1.8 and Na V 1.9 in acute itch signalling.

Acute pruritus occurs in various disorders. Despite severe repercussions on quality of life treatment options remain limited. Voltage-gated sodium channels (Na _V ) are indispensable for transformation and propagation of sensory signals implicating them as drug targets. Here, Na _V 1.7, 1.8 and 1.9 were compared for their contribution to itch by analysing Na _V -specific knockout mice. Acute pruritus was induced by a comprehensive panel of pruritogens (C48/80, endothelin, 5-HT, chloroquine, histamine, lysophosphatidic acid, trypsin, SLIGRL, β-alanine, BAM8-22), and scratching was assessed using a magnet-based recording technology. We report an unexpected stimulus-dependent diversity in Na _V channel-mediated itch signalling. Na _V 1.7 ^-/- showed substantial scratch reduction mainly towards strong pruritogens. Na _V 1.8 ^-/- impaired histamine and 5-HT-induced scratching while Na _V 1.9 was involved in itch signalling towards 5-HT, C48/80 and SLIGRL. Furthermore, similar microfluorimetric calcium responses of sensory neurons and expression of itch-related TRP channels suggest no change in sensory transduction but in action potential transformation and conduction. The cumulative sum of scratching over all pruritogens confirmed a leading role of Na _V 1.7 and indicated an overall contribution of Na _V 1.9. Beside the proposed general role of Na _V 1.7 and 1.9 in itch signalling, scrutiny of time courses suggested Na _V 1.8 to sustain prolonged itching. Therefore, Na _V 1.7 and 1.9 may represent targets in pruritus therapy.